﻿Shader "Custom/DrawLineShader"
{
    Properties
	{
		_Point1("Point1",vector) = (100,100,0,0)
		_Point2("Point2",vector) = (200,200,0,0)
		_LP1("linePoint1",vector) = (300,100,0,0)
		_LP2("linePoint2",vector) = (600,400,0,0)
		_LineWidth("LineWidth",range(1,20)) = 2.0
	
	}
	SubShader
	{
		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			
			#include "UnityCG.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
			};

			struct v2f
			{
				float4 vertex : SV_POSITION;
			};
			float4 _Point1;
			float4 _Point2;
			float4 _LP1;
			float4 _LP2;
			float _LineWidth;		
			
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
			    //绘制圆形，此处半径使用了固定值1000和500,当然大家也可以把他们写成可调的参数
				if( pow((i.vertex.x- _Point1.x ),2) + pow((i.vertex.y- _Point1.y ),2) <1000   )
				{
					return fixed4(0,1,0,1);
				}
				if( pow((i.vertex.x- _Point2.x ),2) + pow((i.vertex.y- _Point2.y ),2) <500   )
				{
					return fixed4(1,0,0,1);
				}

				//绘制直线上两点
				if( pow((i.vertex.x- _LP1.x ),2) + pow((i.vertex.y- _LP1.y ),2) <100   )
				{
					return fixed4(0,0,1,1);
				}
				if( pow((i.vertex.x- _LP2.x ),2) + pow((i.vertex.y- _LP2.y ),2) <100   )
				{
					return fixed4(0,0,1,1);
				}

				//计算点到直线的距离
				float d = abs((_LP2.y-_LP1.y)*i.vertex.x + (_LP1.x - _LP2.x)*i.vertex.y +_LP2.x*_LP1.y -_LP2.y*_LP1.x )/sqrt(pow(_LP2.y-_LP1.y,2) + pow(_LP1.x-_LP2.x,2));
				//小于或者等于线宽的一半时，属于直线范围
				if(d<=_LineWidth/2)
				{
					return fixed4(0.8,0.2,0.5,1);
				}

				//绘制网格直线
				if( (unsigned int)i.vertex.x% (unsigned int)(0.25*_ScreenParams.x)==0 )
				{
					return fixed4(0,0,1,1);
				}
				if( (unsigned int)i.vertex.y% (unsigned int)(0.1*_ScreenParams.x)==0 )
				{
					return fixed4(0,0,1,1);
				}
				//默认返回白色
				return fixed4(1,1,1,1);

			}
			ENDCG
		}
	}
}
